Polydiorganosiloxanes are generally produced by polymerizing a diorganosiloxane such as hydroxyl endblocked dimethyl fluids, dimethyl cyclicsiloxanes, phenylmethyl siloxanes, and others in the presence of a triorganosilyl endblocker. One typical catalyst for this reaction is an acid such as an acid treated montmorillonite clay. For example, U.S. Pat. No. 4,005,023 to Brown and Traver describes linear hydraulic silicone fluids having 2 to 2,000 silicon atoms in the polymer chain. The linear hydraulic silicone fluids can be produced by several methods. One of the methods described comprises equilibrating a silicone fluid (produced from hydrolysis of organohalosilanes) using an acid-treated clay. Another method comprises polymerizing cyclicsiloxanes and mono-functional compounds using an acid catalyst such a FILTROL (an acid clay).
While the acid treated montmorillonite catalyst is effective in producing the polydiorganosiloxane it also creates undesired branching along the polydiorganosiloxane molecule.
Further, U.S. Pat. No. 4,888,405 to Gamon et al., discloses a method for treating organocyclosiloxanes with an acid treated montmorillonite catalyst to reduce hydroxyl content and thus producing organocyclosiloxane-containing mixtures which are suitable as starting materials for silicones having reproducible viscosities. The catalysts employed by Gamon include acid activated bleaching earths and zeolites. Gamon teaches that the catalyst condenses the silanol while the equilibration of the cyclics occurs only to a very small extent.
Although it is fairly well known in the art that acid treated montmorillonite clays may be used to produce certain silicones, the use of cation exchanged acid treated montmorillonite clays in tile production or treatment of polydiorganosiloxanes is relatively unknown. "Solid Acid-Catalyzed Allylation of Acetals and Carbonyl Compounds with Allylic Silanes", Chem. Lett., 1986, (3), 381-384, to Kawai et al. discloses the use of an aluminum cation or proton exchanged montmorillonite to catalyze the reaction between allylic silanes and carbonyl compounds.
It is an object of this invention to show the use of a cation exchanged acid treated montmorillonite clay in the production of polydiorganosiloxanes.
It is further an object of this invention to show the use of a cation exchanged acid treated montmorillonite clay in the production of polydiorganosiloxanes wherein the clay is effective at catalyzing the polymerization of an organosilicon compound having in the molecule at least one silanol group and a triorganosilyl endblocker.
It is further an object of this invention to show the use of a cation exchanged acid treated montmorillonite clay in the production of polydiorganosiloxanes wherein the clay is effective at catalyzing the polymerization of an organosilicon compound having in the molecule at least one silanol group and a diorganocyclicsiloxane.
It is further an object of this invention to show the use of a cation exchanged acid treated montmorillonite clay in the production of polydiorganosiloxanes wherein the clay is effective at catalyzing the polymerization of a diorganocyclicsiloxane and a triorganosilyl endblocker.